The present invention relates generally to heat exchangers such as are employed for various uses in transferring heat between non-mixing fluids and more particularly to improved header constructions for such heat exchangers of the fin and tube type construction.
Heat exchangers of various types are employed in a great variety of applications ranging from extraction of heat from combustion process such as for building heating to cooling of various fluids such as lubricants, compressed gases or the like. One heat exchanger construction commonly employed particularly in applications wherein a gaseous medium is to be passed over the exterior surface thereof is the fin and tube type construction. Typically such fin and tube type heat exchangers will have a plurality of fluid conducting tubes or conduits arranged in parallel side by side rows extending both longitudinally and transversely of the heat exchanger. Headers are generally connected to opposite ends of these tubes to conduct the fluid to the heat exchanger and the cooled fluid back to the source thereof.
In one form, these headers are fabricated from tubing or pipe of a diameter sufficiently large to provide the desired flow capacities. However, in large capacity heat exchangers having multiple longitudinal rows of tubes, it becomes impractical to directly connect each tube to the header. Thus, in such applications intermediate headers are often provided which interconnect transverse rows of tubes and provide a single longitudinal row of tubes for connection to the primary or main header. Such a construction is disclosed in U.S. Pat. No. 3,515,208, issued June 2, 1970 to J. Karmazin. As these intermediate headers are not generally provided with heat radiating fins, they do not provide an effective heat transfer surface area commensurate with the space which they occupy. Thus, in order to provide a heat exchanger having a given efficiency, it is necessary to increase the physical size thereof which necessitates increased costs in the form of additional framing members and further requires additional space for installation of such units.
Space limitations are becoming an ever-increasing problem particularly for heat exchangers which are designed for use in machinery manufactured for the heavy construction industry in that Federal regulations are requiring more and more pollution and noise abatement equipment of various types to be installed on such equipment. As this additional equipment often requires substantial space and further in that it is generally desirable to keep the overall size of such equipment as small as possible, the available space for installation of such heat exchangers is becoming significantly reduced. Further, the addition of such pollution equipment often requires substantial amounts of additional power be drawn from the engine which increases the amount of heat which must be dissipated by the heat exchanger while also restricting the amount of air which may be passed over the heat exchanger. Thus, not only is the available space for installation of such heat exchangers being reduced, but the demands for heat dissipating capacity are increasing. It therefore becomes important to provide heat exchangers having increased operating efficiencies in order to meet these reduced space requirements and increased heat dissipating requirements.
The present invention provides a header construction which overcomes these problems by eliminating the need for the intermediate header member. The present invention provides a base member which allows for direct connection of any number of longitudinally extending rows of tubes directly to the primary or main inlet and outlet headers thereby allowing the space previously consumed by these intermediate header members to be effectively used for additional heat radiating fin members. Further, the unique header construction allows a header to be fabricated of any desired width without concern that the flow capacity thereof may be either excessive or insufficient as the height of the header may be easily modified to provide any desired volume and hence flow rates therein. The header comprises two generally U-shaped channel members one of which has a width slightly less than the width of the other so as to allow the outwardly projecting flange portions thereof to nest between and adjacent to the outwardly projecting flange portions of the other member. A clip member may be employed between these adjacent flange portions and will serve to mechanically secure these adjacent flange portions together prior to and during an oven brazing operation as well as to provide a multisurfaced seal between these members. Alternatively, the adjacent flange portions may be mechanically secured by tack welding and thereafter sealed by a brazing operation. The base channel member is provided with a plurality of tubular projections extending outward therefrom which are adapted to telescopically receive or be received by the respective tubes from the fin and tube construction thereby allowing the fin portions to approach within a close proximity to the header itself. Further, these generally tubular projections are provided with a hydraulic radius at their junction with the base member so as to insure a smooth laminar fluid flow between the header and the tubes. Also, a unique baffle assembly is provided which enables a single header assembly to provide both inlet and outlet header chambers such as may be desirable for two pass counterflow heat exchanger.
Thus, the present invention allows fabrication of a heat exchanger having substantially greater numbers of heat radiating fins and therefore substantially greater capacity for a given size heat exchanger. Further, the header is extremely economical to construct and may be easily fabricated from whatever desired gauge channel or flat formed stock is necessary to resist the pressure forces which will be generated during operation thereof as well as providing a strong frame for supporting and protecting the core. Also, the use of the generally S-shaped clip member insures a high integrity joint as substantial amounts of brazing material will be deposited to create a positive, long-lasting and durable sealing relationship between the adjacent flange members and portions of the clip member.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.